1. Field of the Invention
The present invention relates to an image displaying apparatus that allows an operator to control the display of a digital image or the like as produced by a computer or projector on a screen during the showing of the image at a presentation or a lecture.
2. Background and Related Art
At conventional presentations or lectures, characters or figures are projected on a screen with an overhead projector (OHP), or displayed on a display monitor, to give explanations while showing images of such characters or figures.
The prior art includes apparatus for detecting a predetermined position on a screen indicated by an operator to convert an image into a preferred one so that he/she smoothly can give an explanation. This apparatus is equipped with a light-emitting element at the tip of pointer used by the operator when giving an explanation, the element causing the apparatus to emit light with a switching operation to form an indication point on the screen where the OHP generates an image. The image on the screen is photographed by a different camera, and indication point is detected by light emitted from the image as photographed by the television camera to change the image into another image corresponding to the detected indication point.
However, an apparatus that detects the indication point with a television camera requires an alignment of the image projected by the OHP to the position of the image detected by the television camera as mentioned above. This may cause an error in detection of the indication point. In other words, when the operator (presenter) moves the OHP or the television camera to deviate the projection positions of the image and the detection position of the indication point relative to each other, the position for specifying the indication point will be deviated.
In addition, since the brightness of the image that forms a background is not definite in detecting the position of the indication point from the emitted light, the image projected on the screen may vary the output of the television camera with the result that a bright luminous point is detected by mistake as the indication point. This does not allow a complete determination of the indication point thereby causing an error in recognizing the indication point.
As an apparatus for solving the above problem, thus exists an image displaying apparatus that blinks an indication region (hereinafter referred to as an object) for image conversion on an image projected on a screen by control of a calculator to detect the object indicated by the operator, thereby indicating the conversion of the projected image (IBM Technical Disclosure Bulletin, Vol. 33, No. 6B, November 1990). This technique determines which object has been selected by allowing an operator to select the object by blinking on the screen with an indication device and to detect the blinking indication region with a detector mounted on the indication device.
However, as in the above device, constantly blinking the object to analyze the blinking signal may cause an error in the detection of the object as in the case of detecting the indication point with the television camera.
For example, when the operator moves the indication device, the output of the detector varies with an image on the screen and the orientation of a light detector. In addition, when data such as animated images or the like is displayed on a screen in which data is accompanied by a change in brightness, the output signal of the detector varies at any position where the operator places the indication device as well as in the object. Consequently, even when the object is blinked, the object cannot be determined reliably.
The object of the present invention is to provide an image display apparatus that can accurately detect the object designated by the operator in consideration of the above fact.